Rotaviruses (RV) cause acute gastroenteritis, a disease that requires hospitalization of infants and young children in developed countries, and a frequent cause of death in children less than 5 years of age in developing regions of the world. Studies in the United States, Australia, and Japan have demonstrated that between 34 and 63% of hospitalizations of children for acute diarrheal disease are associated with rotavirus infection. The incidence of hospitalization for rotavirus gastroenteritis in a health maintenance organization in the U.S. was estimated to be 222 per 100,000 in children from 13 to 24 months of age, and 362 per 100,000 in those less than one year. Infection with rotavirus was associated with 63% of all hospitalizations for acute diarrhea in this pediatric population. A review of mortality data in the U.S. from 1973 to 1983 indicated that 500 deaths per year occur in children less than 4 years old due to diarrheal diseases, and that 20 to 80% of excess winter deaths due to diarrhea in the U.S. are associated with rotavirus infections. Rotaviruses are also responsible for substantial proportion of the mortality associated with diarrheal diseases in third world countries. An effective rotavirus vaccine would therefore have a major impact on the health of children in both the developed and developing areas of the world.
Rotaviruses have an inner and outer capsid with a double-stranded RNA genome formed by eleven gene segments. Multiple serotypes have been defined by plaque reduction neutralization tests, and studies of reassortant viruses have demonstrated that two outer capsid proteins, VP7 and VP4, are the determinants of virus serotype. The VP7 protein is coded for by either gene segment 7, gene segment 8 or gene segment 9 of a particular human rotavirus. The location of the VP7 encoding gene may be determined for each specific rotavirus by conventional experimental methods. The VP4 protein is an 88,000 dalton major surface structural protein product of gene 4 of a rotavirus. Like VP7, it functions as a major serotype-specific antigen, operative in serum neutralization (SN) tests, capable of inducing serotype-specific neutralizing antibody, and capable in a mouse system of inducing serotype-specific immune protection against rotavirus disease. In some earlier references, the VP4 was referred to as VP3. After 1988, a change in nomenclature, resulted in the more proper reference to this protein as VP4.
Since the gene segments encoding the VP7 and VP4 proteins segregate independently, it has been proposed that serotyping nomenclature include both the G type, determined by VP7, and the P type, determined by VP4. Most human rotavirus infections in the U.S. are caused by viruses of G types 1, 2, 3, or 4, and P types 1, 2, or 3. However, other human rotavirus types, including for example, type G9, are more prevalent in Asia, Europe and certain third world countries.
A number of animal rotaviruses are attenuated in humans, and have been evaluated as potential live rotavirus vaccines, including the bovine serotype G6 WC3 rotavirus. The WC3 vaccine virus was shown to be immunogenic and non-reactogenic in infants, but was inconsistent in providing protective immunity against human rotavirus infection. It has been suggested that serotype-specific immunity is necessary to include consistent protection against rotavirus diarrhea.
There exists a need to the art for effective vaccines providing protective immunity against rotavirus infection and the severe clinical symptoms associated therewith.
For worldwide distribution of rotavirus vaccines, it is necessary to formulate vaccines such that they are stable under a variety of environmental conditions. Components used to stabilize vaccines are known. However, particular formulations of components useful to stabilize rotavirus vaccines must be determined experimentally. One object of the present invention is present formulations which stabilize rotavirus vaccines.